Not to be confused with Charm glitch.
The Cute Charm exploit, also known as the Cute Charm glitch, is an exploit in Generation IV.
Outside of battle, the ability Cute Charm will cause 2 of 3 wild encounters to be of the opposite gender to the lead Pokémon. This exploit combines the means by which Cute Charm does this with the potential to manipulate one's ID and SID to give the player a very high chance of encountering a Shiny Pokémon, compared to the usual 1 in 8192.
The reason for this is that Cute Charm's effect forces the opponent Pokémon's PID to be one of 25 values when it activates. Each of these values corresponds with one nature. Due to their proximity, if the player's ID xor SID is very low, they will all generate shiny Pokémon.
After obtaining a suitable ID and SID combination, all that needs to be done to generate shiny encounters is to walk around with a Cute Charm Pokémon first in the party. Additionally, when manipulating the RNG for IVs, many more desirable combinations are possible than when not using a Cute Charm lead, or even when using a Synchronize lead.